Improvement of insulin sensitivity in response to exercise training in type 2 diabetes mellitus is associated with vascular endothelial growth factor A expression

Effects of Acute and Chronic Exercise in Hypoxia on Cardiovascular and Glycemic Parameters in Patients with Type 2 Diabetes: A Systematic Review

Kindlovits, Raquel, Alberto Mello da Silva Pereira, Ana Catarina Sousa, João Luís Viana,and Vitor Hugo Teixeira. Effects of acute and chronic exercise in hypoxia on cardiovascular and glycemic parameters in patients with type 2 diabetes: a systematic review. High Alt Med Biol. 23:301-312, 2022. Background: Exercise in hypoxia (EH, decreased oxygen availability) has been proposed as a potential therapeutic intervention to promote angiogenesis and improve glucose metabolism to a greater extent than exercise under normoxia (normal ambient air) in patients with type 2 diabetes (T2D). Currently, there are no studies that systematize the existent evidence. This study aims to systematically review the literature and qualitatively evaluate the effects of acute and chronic EH on cardiovascular and glycemic parameters in T2D patients. Methods: A structured search was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines until March 2021, in the MEDLINE/PubMed, Scopus, and Web of Science databases. The inclusion criteria were as follows: (1) randomized and nonrandomized trials, (2) in complication-free patients with T2D, (3) in which EH was compared with exercise in normoxia or with baseline data, and (4) published in English. Results: Six articles (64 subjects) met the inclusion criteria and were reviewed to data extraction. Four articles investigated the acute effect of EH (33 subjects), and two articles investigated the chronic effect of EH (31 subjects), ranging from 6 to 8 weeks. All studies used a cycle ergometer as exercise. Acute EH benefits insulin sensitivity, blood glucose, vascular endothelial growth factor, and metalloproteinase-9, while chronic EH benefits nitric oxide synthase in erythrocytes, but not brachial artery flow-mediated dilation. Conclusion: Acute EH improves glucose homeostasis in T2D patients, which was not seen with chronic EH. Both acute EH and chronic EH improve angiogenesis regulators, but not vascular function. Despite the putative benefits of EH in patients with T2D, the evidence is still scarce and further research is needed before recommendations can be provided.

Pomegranate juice intake enhances the effects of aerobic training on insulin resistance and liver enzymes in type 2 diabetic men: a single-blind controlled trial

BACKGROUND

Lifestyle interventions are the first-line treatment for Type 2 diabetes mellitus (T2DM), highly prevalent in the community. This study aimed to examine the 8-week separate and combined effects of aerobic training (AT) and pomegranate juice intake (PJI) on insulin resistance and serum levels of liver enzymes, liver enzymes, and insulin resistance in men with T2DM.

METHODS

This study evaluated the alterations of anthropometric indices, insulin resistance, and liver enzymes in 40 middle-aged men (40-50) with T2DM. Participants were randomly assigned into four groups: AT+PJI (n = 10); AT (n = 10); PJI (n = 10), and control (C) (n = 10). The AT program consisted of 60-75% of maximum heart rate (HR_max), 40-60 min/day, and 3 days/wk. Participants in the PJI group consumed 240 ml of pomegranate juice (sugar or additive-free) daily for 8 weeks.

RESULTS

AT+PJI, PJI, and AT groups decreased anthropometric indices, HOMA-IR, and liver enzymes after 8 weeks. In contrast, the C group significantly increased the mentioned variables after the intervention. The result showed that AT+PJI significantly lowered liver enzymes, anthropometric indices, and HOMA-IR than AT or PJI alone. Also, the results of this study showed no significant difference between AT and PJI groups. However, in these groups, significant improvements in these variables were observed compared to the control group.

CONCLUSION

Due to the effect of combined AT+PJI in improving T2DM risk factors, it could be recommended for T2DM patients to prevent increased liver enzymes and insulin resistance.

Glucose Uptake by Skeletal Muscle within the Contexts of Type 2 Diabetes and Exercise: An Integrated Approach

Type 2 diabetes continues to negatively impact the health of millions. The inability to respond to insulin to clear blood glucose (insulin resistance) is a key pathogenic driver of the disease. Skeletal muscle is the primary tissue for maintaining glucose homeostasis through glucose uptake via insulin-dependent and -independent mechanisms. Skeletal muscle is also responsive to exercise-meditated glucose transport, and as such, exercise is a cornerstone for glucose management in people with type 2 diabetes. Skeletal muscle glucose uptake requires a concert of events. First, the glucose-rich blood must be transported to the skeletal muscle. Next, the glucose must traverse the endothelium, extracellular matrix, and skeletal muscle membrane. Lastly, intracellular metabolic processes must be activated to maintain the diffusion gradient to facilitate glucose transport into the cell. This review aims to examine the physiology at each of these steps in healthy individuals, analyze the dysregulation affecting these pathways associated with type 2 diabetes, and describe the mechanisms by which exercise acts to increase glucose uptake.

CD44, a Predominant Protein in Methylglyoxal-Induced Secretome of Muscle Cells, is Elevated in Diabetic Plasma

Methylglyoxal (MG), a glycolytic intermediate and reactive dicarbonyl, is responsible for exacerbation of insulin resistance and diabetic complication. In this study, MG-induced secretome of rat muscle cells was identified and relatively quantified by SWATH-MS. A total of 643 proteins were identified in MG-induced secretome, of which 82 proteins were upregulated and 99 proteins were downregulated by more than 1.3-fold in SWATH analysis. Further, secretory proteins from the classical secretory pathway and nonclassical secretory pathway were identified using SignalP and SecretomeP, respectively. A total of 180 proteins were identified with SignalP, and 113 proteins were identified with SecretomeP. The differentially expressed proteins were functionally annotated by KEGG pathway analysis using Cytoscape software with plugin clusterMaker. The differentially expressed proteins were found to be involved in various pathways like extracellular matrix (ECM)-receptor interaction, leukocyte transendothelial migration, fluid shear stress and atherosclerosis, complement and coagulation cascades, and lysosomal pathway. Since the MG levels are high in diabetic conditions, the presence of MG-induced secreted proteins was inspected by profiling human plasma of healthy and diabetic subjects (n = 10 each). CD44, a predominant MG-induced secreted protein, was found to be elevated in the diabetic plasma and to have a role in the development of insulin resistance.

Hypoxia and exercise interactions on skeletal muscle insulin sensitivity in obese subjects with metabolic syndrome: results of a randomized controlled trial

BACKGROUND

Physical activity improves insulin sensitivity in obesity. Hypoxia training is claimed to augment this effect. We tested the hypothesis that normobaric hypoxia training would improve insulin sensitivity in obese patients with metabolic syndrome.

METHODS

In a randomized controlled trial, 23 obese men with metabolic syndrome who were not informed of the FiO₂ conditions underwent a 6-week physical exercise intervention under ambient (n = 11; FiO₂ 21%) conditions or hypoxia (n = 12; FiO₂ 15%) using a normobaric hypoxic chamber. Three 60-min sessions of interval training were performed each week at 60% of individual V̇O_2max. Assessment of myocellular insulin sensitivity by euglycemic hyperinsulinemic clamp was performed in 21 of these subjects before and after 6 weeks of training. Comprehensive phenotyping also included biopsies of subcutaneous adipose tissues.

RESULTS

The intermittent moderate physical exercise protocol did not substantially change the myocellular insulin sensitivity within 6 weeks under normoxic conditions (ISI_Clamp: 0.035 (IQR 0.016-0.075) vs. 0.037 (IQR 0.026-0.056) mg* kg^-1 *min^-1/(mU* l^-1); p = 0.767). In contrast, ISI_Clamp improved during hypoxia training (0.028 (IQR 0.018-0.035) vs. 0.038 (IQR 0.024-0.060) mg * kg^-1 *min^-1/(mU *l^-1); p < 0.05). Between group comparison of ISI_Clamp change revealed a small difference between groups (Cohen's d = 0.26). Within the hypoxic group, improvement of ISI_Clamp during training was associated with individual increase of circulating vascular endothelial growth factor (VEGF) levels (r = 0.678, p = 0.015), even if mean VEGF levels were not modified by any training condition. Atrial natriuretic peptide (ANP) system components were not associated with increased ISI_Clamp during hypoxic training.

CONCLUSIONS

Physical training under hypoxic conditions could partially augment the favorable effects of exercise alone on myocellular insulin sensitivity in obese men with metabolic syndrome. Concomitant changes in VEGF might represent an underlying pathophysiological mechanism.

Impact of Exercise on Inflammatory Mediators of Metabolic and Vascular Insulin Resistance in Type 2 Diabetes

The development of obesity is cornerstone in the etiology of metabolic and vascular insulin resistance and consequently exacerbates glycemic control. Exercise is an efficacious first-line therapy for type 2 diabetes that improves insulin action through, in part, reducing hormone mediated inflammation. Together, improving the coordination of skeletal muscle metabolism with vascular delivery of glucose will be required for optimizing type 2 diabetes and cardiovascular disease treatment.

Chronic Exercise Improves Mitochondrial Function and Insulin Sensitivity in Brown Adipose Tissue

The aim of the present work was to study the consequences of chronic exercise training on factors involved in the regulation of mitochondrial remodeling and biogenesis, as well as the ability to produce energy and improve insulin sensitivity and glucose uptake in rat brown adipose tissue (BAT). Male Wistar rats were divided into two groups: (1) control group (C; n = 10) and (2) exercise-trained rats (ET; n = 10) for 8 weeks on a motor treadmill (five times per week for 50 min). Exercise training reduced body weight, plasma insulin, and oxidized LDL concentrations. Protein expression of ATP-independent metalloprotease (OMA1), short optic atrophy 1 (S-OPA1), and dynamin-related protein 1 (DRP1) in BAT increased in trained rats, and long optic atrophy 1 (L-OPA1) and mitofusin 1 (MFN1) expression decreased. BAT expression of nuclear respiratory factor type 1 (NRF1) and mitochondrial transcription factor A (TFAM), the main factors involved in mitochondrial biogenesis, was higher in trained rats compared to controls. Exercise training increased protein expression of sirtuin 1 (SIRT1), peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) and AMP-activated protein kinase (pAMPK/AMPK ratio) in BAT. In addition, training increased carnitine palmitoyltransferase II (CPT II), mitochondrial F1 ATP synthase α-chain, mitochondrial malate dehydrogenase 2 (mMDH) and uncoupling protein (UCP) 1,2,3 expression in BAT. Moreover, exercise increased insulin receptor (IR) ratio (IRA/IRB ratio), IRA-insulin-like growth factor 1 receptor (IGF-1R) hybrids and p42/44 activation, and decreased IGF-1R expression and IR substrate 1 (p-IRS-1) (S307) indicating higher insulin sensitivity and favoring glucose uptake in BAT in response to chronic exercise training. In summary, the present study indicates that chronic exercise is able to improve the energetic profile of BAT in terms of increased mitochondrial function and insulin sensitivity.